Hypergolic solid fuels of high storage stability for hybrid rocket engines and process for making the same

ABSTRACT

A hypergolic solid fuel of high storage stability for hybrid rocket engines, comprising incorporated in a small amount of a binder a combination of compounds extremely rich in hydrogen and rich in nitrogen as compared to the contents in carbon, said nitrogen being in the form of cyano- or hydrazine groups and capable of releasing high energy upon contact with an oxidizer. The invention also relates to a process for making the fuels.

States atem Sarten et a1.

[451 May 16, 1972 HYPERGOLIC SOLID FUELS OF HIGH STORAGE STABILITY F ORHYBRID ROCKET ENGINES AND PROCESS FOR MAKING THE SAME Inventors: PaulaSarten, Munich; Winfried Mair,

Riemerling, both of Germany Assignee: Messerschmitt-Bolkow, Gesellschaftmit beschrankter Haftung, Ottobrunn near- Munich Germany Filed: Jan. 16,1969 Appl No.: 791,803

Foreign Application Priority Data Jan. 20, 1968 Germany ..P 16 46 310.8

U.S. Cl ..149/19, 149/36, 149/87, 149/20, 260/308 R, 60/219 Int. Cl...C06d 5/10 Field of Search ..l49/36, 87, 19, 20; 260/308 R; 60/219 [56]References Cited UNITED STATES PATENTS 3,338,762 8/1967 Oja ..l49/l93,398,215 8/1968 Spenadel et a1. 3,403,062 9/1968 Ponnell et a1.3,499,289 3/1970 Olsen ..60/218 Primary ExaminerCarl D. QuarforthAssistant Examiner-E. A. Miller AttorneyMcGlew and Toren 57 ABSTRACT 11Claims, No Drawings I'IYPERGOLIC SOLID FUELS OF HIGH STORAGE STABILITYFOR HYBRID ROCKET ENGINES AND PROCESS FOR MAKING THE SAME SUMMARY OF THEINVENTION The present invention relates to hypergolic solid fuels ofhigh storage stability for hybrid rocket engines and to a process ofproducing the fuels.

Hypergolic denotes the capacity of self-ignition upon contact withanother chemical,

The known, presently used solid fuels for hybrid engines consist ofpolyethylene, polyester, polyurethanes, polyamides and others, which arerendered hypergolic by the addition of metals, hydrides, ferrocene andthe like, when contacted with gaseous or liquid oxidizers. Upon reactionwith the second component, the gaseous or liquid oxidizer, thecombustion process leads to an undesirable deposition of carbon in theform of soot and/or solid oxidation products and causes surfaceincrustations, thus leading to a poor performance of the fuel. Moreover,a desired re-ignition is thus made more difficult, if not impossible,since due to carbonization or incrustation of the binder, a surfacelayer will result which prevents reignition or will at least makere-ignition unreliable. Moreover, due to the incomplete combustion, partof the combustible substance is entrained unburned by the effluent anddeposited together with the soot, whereby the specific efficiency isdecreased.

Attempts have been made to overcome these difficulties by addition ofmoderate amounts of oxidizers or by incorporation to nitro groups intothe fuel, thereby enhancing combustion and, sometimes, facilitatingreignition. However, by these additions and by the introduction of nitrogroups, the stability of such solid fuels during storage is considerablyimpaired; furthermore, by incorporation of high energy substances, thechemical stability of the fuel may be endangered.

It is the object of the present invention to overcome the existingshortcomings of known solid rocket fuels for hybrid rocket engines.

It is another object of the invention to provide solid rocket fuels forhybrid engines which will ensure re-ignition of the fuels after eachcombustion and which, moreover, are of higher energy that will beutilized to the highest degree.

It is yet another object to provide solid rocket fuels which will bevery stable during storage and handling.

lt is also an object to provide a process for producing the solid rocketfuels above mentioned.

Other objects and advantages of the invention will become apparent fromthe detailed description hereinbelow.

The solid fuels according to the invention comprise a combination ofcomponents which upon reaction with oxygen is capable of releasing anextremely high percentage of hydrogen and a high percentage of highenergy nitrogen, both calculated on the carbon present, the nitrogenbeing present in the form of hydrazine of cyano groups.

Solid fuels according to the invention may have the followingcompositions:

All parts are by weight.

1. 20-90 parts of 4-aminodihydrazino-l ,2,4-triazole, as well as theacid, neutral and basic carbonate of 4- aminodihydrazino-l,2,4-triazole,also the neutral and basic thiocyanate of 4-aminodihydrazino-l,2,4-triazole, primarily the neutral and basic cyanide of4-amino-dihydrazino-l,2,4- triazole;

moreover:

2. 5 parts of binder, mostly free of oxygen, basically consisting ofhydrocarbon polymers, if de-sired combined with terpene resins and, insome cases, up to 3. 50 parts of additives of the type of powderedmetals, e.g. Be, Mg, Al, B, Zr, etc. or hydrides of Li, Na, Be, K, etc.or alanates and boranates of Li, Na, K, Be, etc. or alkyls of Li, Na, K,Be, Al, Mg, Zn, etc. or colloids of Li, Na, K, etc. or a cyanoderivative or substances of the type of ferrocenes, nickelo orcobaltocenes, etc., and

min

4. 0. l 10 parts of other additives of the type of plasticizers,catalysts and/ or surfactants. Another embodiment of the inventioncomprises solid fuels of the following compositions:

1. l0 parts of triaminoguanidine, as well as the acid, neutral and basiccarbonate of triaminoguanidine, also the neutral and basic thiocyanateof triaminoguanidine, primarily the neutral and basic cyanide oftriaminoguanidine, furthermore:

2. 5 20 parts of binder, based on polybutadiene or epoxy resins modifiedwith, natural resins based on terpenes, if desired also up to 3. 50parts of additives of the type of powdered metals, e. g. Be, Mg, Al, B,Zr, etc. or hydrides of Li, Na, Be, K, etc. or alanates and boranates ofLi, Na, K, Be,etc. or alkyls of Li, Na, K, Be, Al, Mg, Zn, etc. orcolloids of Li, Na, K, etc. or ferrocenes, nickeloor cobaltocenes or acyano derivative of the type of dihydrazinodicyanodiimine; finally, ifdesired,

4. 0.1 10 parts of other additives of the type of a plasticizer,catalyst and/or surfactant.

It should be noted that the binder is present in comparatively smallamounts.

In the preparation of the solid fuels according to the invention, we mayproceed in different ways.

Either the oxygen-free binder of the type indicated above is mixed atnormal temperature with the triaminoguanidine and/or a derivativethereof, or the 4-aminodihydrazino-1,2,4- triazole and/or a derivativethereof, and the additives are admixed last; or,

triaminoguanidine and its derivatives or 4-aminodihydrazino-l,2,4-triazole and its derivatives are first mixed withthe additives and the binder is added last; or,

the binder may first be mixed with the additives, and thetriaminoguanidine or its salts, or the 4-aminodihydrazino-1,2,4-triazole or its salts are added last.

Other additives of the type of copper chromite, plasticizer andsurfactant are finally added.

In the following, the invention will be more fully described by a numberof examples which are given by way of illustration, but not oflimitation. Parts are by weight.

EXAMPLE 1 About 25 parts of 4-aminodihydrazino-l ,2,4-triazo1e about 40parts of triaminoguanidine or triaminoguanidine thiocyanate About 25parts of NaAlH,

About 8 parts of binder About 1-2 parts of various additives (in thenature plasticizers, catalysts, hardeners). EXAMPLE 2 About 67.5 partsof triaminoguanidine cyanide About 20 parts of Mg powder About 7.5 partsof binder About 1-2 parts of various additives (in the natureplasticizers, catalysts, hardeners). EXAMPLE 3 About 10 parts of4-aminodihydrazino-l ,2,4-triazole About 50 parts of triaminoguanidinecyanide About 20 parts of dihydrazinodicyanodiimine About 10 parts ofbinder About 1-2 parts of various additives (in the nature plasticizers,catalysts, hardeners). EXAMPLE 4 About 70 parts of 4-aminodihydrazino-l,2,4-triazole About 20 parts of Na colloid About 10 parts of binderAbout l-2 parts of various additives (in the nature plasticizers,catalysts, hardeners). EXAMPLE About 70 parts of4-aminodihydrazino-l,2,4-triazole thiocyanate About 25 parts of NaAll-I,

About 8 parts of binder About l2 parts of various additives (in thenature of plasticizers, catalysts, hardeners). EXAMPLE 6 About 30 partsof 4-aminodihydrazino-l,2,4-triazole cyanide About 30 parts oftriaminoguanidine cyanide About 20 parts of dihydrazinodicyanidediimineAbout 20 parts of NaAlH About 8 parts of binder About l-2 parts ofvarious additives (in the nature of plasticizers, catalysts, hardeners).EXAMPLE 7 About 40 parts of 4-aminodihydrazino-l,2,4-triazole About 50parts of triaminoguanidine cyanide About 20 parts ofdihydrazinodicyanodiimine About 20 parts of NaAll-l,

About 15 parts of binder About 1-2 parts of various additives (in thenature of plasticizers, catalysts, hardeners).

As oxidizers we may use gaseous or liquid substances of the type offluorine derivatives, such as ClF ClF and others, liquid oxygen, etc., HN 0 preferably however HNO WFNA (white fuming nitric acid), RFNA (redfuming nitric acid plus 1 percent HF) or perchloric acid which willreact hypergolically with the mentioned fuels and make re-ignitionpossible.

The solid fuels according to the invention burn with a flame whichbecomes extinguished when the engine is cut off, without causingincrustations or soot deposition and without the risk of explosion.Thus, upon restarting the engine, i.e. upon renewed addition of theoxidizer, dependable re-ignition is guaranteed.

As compared to known rocket fuels, the fuels according to the inventionare distinguished by an extremely high amount of hydrogen and a highamount of nitrogen in the form of hydrazineor cyano groups, calculatedon carbon. The mentioned substances generate a high combustiontemperature and due to their high energy cause a considerably increasedrate of reaction and therewith increased rate of propulsion.

What is claimed is:

1. A hypergolic solid propellant charge of high storage stability forhybrid rocket engines, comprising about 8-l5 percent of substantiallyoxygen free binder comprising polyhydrocarbons and a major amount of acompound selected from the group consisting of 4-aminodihydrazinel,2,4-triazole 4-aminodihydrazinol ,2,4-triazole acid carbonate4-aminodihydrazinol ,2,4triazole carbonate 4-aminodihydrazino1,2,4-tiazole thiocyanate 4-aminodihydrazino-l ,2,4-tiazole cyanidetriaminoguanidine triaminoguanidine acid carbonate triaminoguanidinecarbonate triaminoguanidine thiocyanate triaminoguanidine cyanide.

2. The propellant charge according to claim 1 further comprisingdihydrazinodicyanodiimine.

3. The propellant charge according to claim 1, wherein the binder isadmixed with natural resins based on terpenes.

4. Solid fuel according to claim 1, comprising About 25 parts by weightof 4-aminodihydrazino-l ,2,4-

mun

triazole about 40 parts by weight of triaminoguanidine thiocyanate about25 parts by weight of NaAlI-l, and about 8 parts by weight of saidbinder. 5. Solid fuel according to claim 1, comprising about 67.5 partsby weight of triaminoguanidine cyanide about parts by weight of Mgpowder and about 7.5 parts by weight of said binder. 6. Solid fuelaccording to claim 1, comprising about 10 parts by weight of4-aminodihydrazinol ,2,4 triazole about 50 parts by weight oftriaminoguanidine cyanide about 20 parts by weight ofdihydrazinodicyanodiimine and about 10 parts by weight of said binder.7. Solid fuel according to claim 1, comprising about 70 parts by weightof 4-aminodihydrazino-l ,2,4-triazole thiocyanate about 20 parts byweight of Na colloid and about 10 parts by weight of said binder.

8. Solid fuel according to claim 1, comprising about 70 parts by weightof 4-aminodihydrazinol ,2,4-

triazole cyanide about parts by weight of NaAlH, and

about 8 parts by weight of said binder.

9. Solid fuel according to claim 1, comprising about parts by weight of4-aminodihydrazinol ,2,4-

triazole about 30 parts by weight of triaminoguanidine cyanide about 20parts by weight of dihydrazinodicyanodiimine about 20 parts by weight ofNaAll-l and about 8 parts by weight of said binder.

10 Solid fuel according to claim 1, comprising about parts by weight of4-aminodihydrazinol ,2,4-

triazole about parts by weight of triaminoguanidine cyanide about 20parts by weight of dihydrazinodicyanodiimine about 20 parts by weight ofNaAlI-l, and about 15 parts by weight of said binder.

11. A process for producing a hypergolic propellant charge for hybridrocket engines, which comprises the steps of incorporating at normaltemperature into a viscous prepolymer of a substantially oxygenfreebinder comprising polyhydrocarbon a compound selected from the groupconsisting of 4-aminodihydrazine-l ,2 ,4-triazole 4-aminodihydrazinol,2,4-triazole acid carbonate 4-aminodihydrazino-1,2,4-triazole carbonate4-aminodihydrazino-l ,2,4-triazole thiocyanate4-aminodihydrazini-1,2,4-triazole cyanide triaminoguanidinetriaminoguanidine acid carbonate triaminoguanidine acid carbonatetriaminoguanidine thiocyanate triaminoguanidine cyanide mixing the saidbinder and said compound, while excluding oxygen, adding further highenergy releasing compounds, and further admixing additives of the natureof a catalyst and a plasticizer, completely mixing the entire mixture,and finally causing hardening of the so prepared propellant.

2. The propellant charge according to claim 1 further comprisingdihydrazinodicyanodiimine.
 3. The propellant charge according to claim1, wherein the binder is admixed with natural resins based on terpenes.4. Solid fuel according to claim 1, comprising About 25 parts by weightof 4-aminodihydrazino-1,2,4-triazole about 40 parts by weight oftriaminoguanidine thiocyanate about 25 parts by weiGht of NaAlH4 andabout 8 parts by weight of said binder.
 5. Solid fuel according to claim1, comprising about 67.5 parts by weight of triaminoguanidine cyanideabout 20 parts by weight of Mg powder and about 7.5 parts by weight ofsaid binder.
 6. Solid fuel according to claim 1, comprising about 10parts by weight of 4-aminodihydrazino-1,2,4-triazole about 50 parts byweight of triaminoguanidine cyanide about 20 parts by weight ofdihydrazinodicyanodiimine and about 10 parts by weight of said binder.7. Solid fuel according to claim 1, comprising about 70 parts by weightof 4-aminodihydrazino-1,2,4-triazole thiocyanate about 20 parts byweight of Na colloid and about 10 parts by weight of said binder. 8.Solid fuel according to claim 1, comprising about 70 parts by weight of4-aminodihydrazino-1,2,4-triazole cyanide about 25 parts by weight ofNaAlH4 and about 8 parts by weight of said binder.
 9. Solid fuelaccording to claim 1, comprising about 30 parts by weight of4-aminodihydrazino-1,2,4-triazole about 30 parts by weight oftriaminoguanidine cyanide about 20 parts by weight ofdihydrazinodicyanodiimine about 20 parts by weight of NaAlH4 and about 8parts by weight of said binder. 10 Solid fuel according to claim 1,comprising about 40 parts by weight of 4-aminodihydrazino-1,2,4-triazoleabout 50 parts by weight of triaminoguanidine cyanide about 20 parts byweight of dihydrazinodicyanodiimine about 20 parts by weight of NaAlH4and about 15 parts by weight of said binder.
 11. A process for producinga hypergolic propellant charge for hybrid rocket engines, whichcomprises the steps of incorporating at normal temperature into aviscous prepolymer of a substantially oxygenfree binder comprisingpolyhydrocarbon a compound selected from the group consisting of4-aminodihydrazine-1,2,4-triazole 4-aminodihydrazino-1,2,4-triazole acidcarbonate 4-aminodihydrazino-1,2,4-triazole carbonate4-aminodihydrazino-1,2,4-triazole thiocyanate4-aminodihydrazini-1,2,4-triazole cyanide triaminoguanidinetriaminoguanidine acid carbonate triaminoguanidine acid carbonatetriaminoguanidine thiocyanate triaminoguanidine cyanide mixing the saidbinder and said compound, while excluding oxygen, adding further highenergy releasing compounds, and further admixing additives of the natureof a catalyst and a plasticizer, completely mixing the entire mixture,and finally causing hardening of the so prepared propellant.